Search Documents

By Don W. Murphy, Don M. Larsen

Advanced process control has been implemented at the Jerritt Canyon Mill. Plant production prior to 1997 was limited by grind circuit capacity. The installation of additional mill horsepower and an optimizing supervisory control system achieved a throughput increase in excess of 12 percent. The controller application utilized a seamlessly integrated fuzzy logic expert system for real-time mill control coupled with a neural network predictor for closed-loop feedback of particle size constraints. In late 1998, a second supervisory controller was installed to operate the fluidized bed roasters. The second controller optimized roasting conditions, increased plant throughput and improved metallurgical recovery.

Jan 1, 2000

By Jean-Luc Cornet

As modern conveyors are increasing in size and complexity, their control requirements are becoming more and more critical. In addition to the safety and equipment protection requirements, control systems are now called to implement intelligent drive controls derived from dynamic analysis modelling, as well as to provide fast and accurate diagnostics while keeping operator controls simple. These requirements led to the development of a new and innovative approach to control system development. This paper describes the control philosophy used by Conveyor Dynamics, Inc. (CDI) and some of the key features of our approach to the architecture of control systems.

Jan 1, 1993

By A. K. Bakshi, Komar S. Kawatra

A plant trial of a new on-line pressure vessel rheometer for slurries, developed at Michigan Technological University, was carried out at a nearby copper concentrator. The rheometer measured the flow curves (shear stress vs. shear rate) of chalcocite slurries. Viscosity of non-Newtonian slurries changes with shear rate and so, for such slurries viscosity measurement at a single shear rate (often seen in the literature for grinding and classification studies) cannot be correlated to process performance. For these slurries, viscosity at various shear rates can be measured from flow curves generated by the pressure vessel rheometer. Other rheological properties, such as flow type and yield stress can be determined by this rheometer to better characterize the slurries. The slurry at the copper concentrator consisted of ground chalcocite ore. The solids content in the slurry varied between 30-60 % by weight. Top size of the particles was 125 micron, and 80% passing size was 34 micron. Measurements by the pressure vessel rheometer showed that most of the slurries had pseudoplastic flow at shear rates below -3000 sec-l, where the viscosity of the slurry decreased with increase in shear rate. Above -3000 sec-l, like a Newtonian fluid, the viscosity of the slurry remained steady. Flow curves and viscosity from the pressure vessel rheometer were verified with a Brookfield viscometer and a vibrating sphere viscometer, and the results were found to be accurate.

Jan 1, 1997

By David M. Shaw, John C. Franklin

A 32-channel warning system for high working level, fan operation, and airlock-doors has been constructed. The working level monitors have a microcomputer for accumulating the pulses, converting to working level, and triggering an alarm at a variable set point and at one working level. The system also detects when underground fans lose power or air doors are open. The system can detect changes in air velocity which indicate surface fan failures or changes in the ventilation system. Using this alarm system, the ventilation engineer will be alerted prior to excessive levels of radon daughters being reached so corrective action can be taken.

Jan 1, 1981

By P. Bevilacqua, G. Vallebuona

Empirical models are now used for predicting the performance of hydrocyclones in terms of capacity. cut size (d50.c), water split and partition curve. These models (such as the model by Lynch and Rao and the model he Plitt) were developed and checked for hydrocylones with diameters larger than 4 in. However, for smaller-diameter hydrocyclones, little empirical modeling has been done. This paper reports on an extended experimental research program on small hydrocyclones. For these cyclones, the suitability of existing empirical models was investigated and their accuracy was compared. To improve the predictive capability of these models to small cyclones modifications to the equations are proposed.

Jan 1, 1996

By Harold E. Goetzman, Blair R. Benner, Shaolin Zhong, Rodney L. Bleifuss

A commercial high pressure roller press (KHD 90125) was installed at the Coleraine Minerals Research Laboratory for testing in October, 1994. Pilot plant evaluation of the high pressure roller press has shown that it can be used as an alternative to the rod mill for the comminution of taconite. A series of pilot plant tests were run to compare roller press products to rod mill products in a simulated taconite flowsheet using magnet separation and closed circuit ball milling. Further investigation of a hybrid grinding system, roller press crushing followed by ball mill grinding, indicate that the combination may represent the most energy efficient system for taconite processing.

Jan 1, 1998

By Daniel L. Hanson

This paper presents case histories of the construction of four large diameter circular shafts using reinforced concrete ring beams as the primary internal support system. The case histories pertain to concrete ring beam systems which have been successfully used in shafts up to 130 feet in diameter and 75 feet deep. Soldier pile and lagging, and driven steel piling earth retaining systems using ring beams, are discussed together with the cost savings associated with using concrete ring beams. Soil conditions encountered at the case history sites are discussed together with the development of design criteria for each shaft. Instrumentation data obtained at one site are also presented.

Jan 1, 1987

By W. Kennedy Gauger, Tim Oolman, Debra L. Bisson

Radian Corporation (Radian) has developed a process for treating Cr(V1)-contaminated soils that involves: 1) soil washing using an alkaline extractant, 2) biological reduction of Cr(V1) to Cr(II1) in the soil wash effluent, and 3) separation of Cr(II1) from the biologically treated effluent. Biological treatment has been demonstrated for immobilized cells in fluidized bed bioreactors and suspended cells in slurry bioreactors for Cr(V1) levels ranging from 30 to 600 mg/L which have been reduced to non-detectable levels (< 0.05 mg/L; method detection limit [MDL]) during hydraulic residence times as short as 12 hours. The resulting Cr(II1)-containing effluent stream was chemically treated to precipitate chromium hydroxide for removal by physical separation.

Jan 1, 1995

By Thomas E. McNider

Preliminary studies were conducted at Jim Walter Resources, Inc. Blue Creek No. 3 Mine to determine the influence propane operated heaters exert on the mine ventilation system when two of three intake airshafts were heated. During initial use of the heaters, it was found that change in density caused by heating a portion of the air at two of three intake shafts altered under- ground air flow changes sufficient to be considered a violation of Part 75.322 of the Federal Coal Mine Health and Safety Act of 1969 as amended by Public Law 95.164. The primary concern was to accurately define the problem in order to derive a workable solution.

Jan 1, 1980

By P. L. Webster, S. D. Thompson

The Coal Mine Belt Capacity Simulator (CMBCS) was originally developed to provide an improved belt capacity simulation through more detailed, flexible and realistic modeling of belt loading. While this model offered improved capacity design for conveyor belts and surge bins, it lacked the capability to simulate some key protection and segregation applications for bunkers. Recently, CMBCS was extended so that these latter bunker applications could be considered. In addition, a fear minor extensions were made to improve the model&apos;s flexibility and of efficiency. These various extensions and the steps taken to verify and validate them are described. The associated modifications in the model&apos;s input and output as well as the model&apos;s current requirements and availability are also discussed.

Jan 1, 1992

By J. A. Brierley, Arpad E. Torma, Victor C. Storhok, C. L. Brierley, Batric Pesic

Chemical and electrochemical studies were performed during bioleaching of cobaltite concentrate with Thiobacillus ferrooxidans. The two principal minerals present in the concentrate were pyrite and cobaltite (CoAsS). During chemical studies, the effect of pH on dissolution rates was examined under uncontrolled and pH-controlled conditions. It was found that in the pH range 1.5-3.0 there was no pH effect if the initial pH was not controlled (maintained). When the initial pH was controlled, the leaching of Co, As, and Fe depended strongly on pH. Electrochemical studies were performed by using cyclic voltammetry and constant potential techniques. A sequential reaction mechanism was proposed for dissolution of cobaltite.

Jan 1, 1993

By J. C. Norman

The United States was the world&apos;s largest producer and consumer of boron compounds during 1994. According to US Bureau of Mines (USBM) estimates, boron mineral concentrate and chemical production in the United States totaled about 1.05 Mt (1.15 million st), yielding 560 kt (617,000 st) of B203, for a total estimated value of $370 million. This production level was about 2% less than 1993 revised figures. The United States continued to provide nearly all of its own boron supply while maintaining a strong position as a source of sodium borate products and boric acid for export. Domestic employment in the mining and beneficiation of boron products during 1994 was 900 people, about the same as in 1993. USBM estimated total world production of boron of about 2.3 Mt (2.5 million st), yielding 1.1 Mt (1.2 million st) of B203. World production during 1994 was about the same as during 1993. USBM estimates US reserves to be about 210 Mt (231 million st) of ore and world reserves to be about 630 Mt (694 million st) of ore.

Jan 1, 1995

By H. M. von Seebach, M. P. Trubeljal, L. G. Austin

Six US coals and a crystalline quartz were tested in an instrumented laboratory high-pressure grinding rolls machine equipped with 100-mm-diam. rolls. The machine was choke-fed to maximize the capacity. As expected, the specific capacity decreased with increased grinding pressure for each material tested. Among the six coals, there were significant differences in the critical angle of nip, the effective feed porosity and the variation of strain at the gap relative to the grinding pressure. Although a precise correlation was not obtained, the overall effect of these factors was that, at a given grinding pressure, the specific capacity increased as the Hardgrove grindability index of the coal increased. The relationship between the specific capacity and the grinding pressure for a given coal was independent of feed size down to 150 µm. However, smaller feed sizes produced anomalous results, and the flow within the feed hopper was restricted.

Jan 1, 1996

By Robert L. Sundeen, Richard V. Wenberg

Service vehicles, often called support vehicles or auxiliary vehicles, are used in secondary functions to support production activities such as loading, drilling, and timbering. Probably the most common support vehicles are the personnel carriers used to move miners to and from work areas. Utility designs are used to transport supplies and various less mobile equipment. Specific application designs are used for special work such as explosives transportation and loading, equipment maintenance, and equipment lubrication. PERSONNEL CARRIERS Personnel carriers are available in a wide variety of sizes and configurations. Some are two-wheel drive, though most are four-wheel drive. Smaller versions carry at least two men and usually have sufficient capacity to carry a small payload of supplies or equip¬ment. The American Motor&apos;s 05 Jeep, equipped with an optional diesel engine, has been adapted successfully for this light duty. Larger personnel carriers with ca¬pacities of 12 to 20 or more men currently are available, as shown in Fig. 1. The designs often are customized to the operating characteristics of each mine. All meet the latest federal requirements for rollover protection, emergency brake systems, etc. UTILITY VEHICLES Utility vehicles are adaptable to numerous duties. Probably the most common are ordinary haulers with a flat bed or low-sided box. They are used for hauling supplies and equipment from one point to another. Some occasionally are used for towing and may pull one or more trailers. Fig. 2 shows a typical utility truck. SPECIAL-APPLICATION VEHICLES Special-application vehicles are possibly the most important of all support types since these vehicles di¬rectly support and maintain production equipment. Such vehicles are available in a wide variety of sizes, mechanical functions, and operating specifications. Most versions are four-wheel drive and articulated. Among the more common vehicles are explosive haulers and loaders, mechanic&apos;s trucks, lubrication trucks (Fig. 3), and special carriers. TYPICAL APPLICATIONS Development Utility haulers are essential in trackless operations to bring supplies to advancing headings. Some utility haulers may be dedicated to bringing in steel sets and may be equipped with boom lifts to unload heavy sup¬ports or even place them as required. A rockbolt hauler may have a boom-mounted operator&apos;s basket which can be used for bolt installation or inspection. Various mechanic&apos;s trucks and pipe trucks service the heading to keep power, air, water, and ventilation at the face and to keep face equipment at maximum utilization. Production Production operations require a variety of support equipment. Because of the larger crew size brought about by the addition of the production force, personnel carriers play a greater role. Correspondingly, steel¬support hauling equipment and bolting trucks usually see limited application. PRODUCTION UNITS Capacity Personnel carriers are available to carry almost any number of people desired. Likewise, other types of carriers or haulers can and are built to fit specific re¬quirements. Physical size, capacity, and operating char¬acteristics can be varied to fit any size of opening and operating condition. Generally, articulated models offer greater maneuverability than straight frame-axle steer designs. Most vehicles of this type are lower in power than production units, generally under 74.6 kW (100 hp). Operating performance still compares favorably to that of production equipment, i.e., the support vehicles can travel at equivalent speeds on the various mine gradients. Manpower Auxiliary vehicles should require only a single opera¬tor. Specific application vehicles may require more than one person. For example, ventilation trucks usually require a crew of two where pipe must be installed.

Jan 1, 1982

By William C. Cooley

Modern tunnel boring machines are subject to excessive cutter wear and bearing failures when used in hard and abrasive rock. In very hard rock, the high cost of cutter and bearing replacement, combined with slower excavation progress, make it more economical to drive tunnels by conventional drill and blast methods. The use of high pressure water jets to break rock provides a promising alternative. Experimental data indicate that the specific energy (the energy expended per unit volume of rock broken) decreases as the water jet pressure increases. Continuous jets are generally limited to pressures below 100,000 psi, whereas pulsed jets from a water cannon can attain much higher pressures. Therefore, the Federal Railroad Administration of the U. S. Department of Transportation has sponsored the design (Ref. 1 & 2) and the fabrication and testing (Ref. 3 & 4) of a water cannon to determine its effectiveness in rock disintegration at very high pressures. This paper reports the results of laboratory tests with pulsed jets against large rock samples at pressures of 125,000 to 650,000 psi and field tests against dolomitic limestone and granitic gneiss at pressures near 450,000 psi. Although initial tests were made with a small nozzle, operating at off-design conditions (Ref. 4), this paper only covers results with the full-size nozzle, including 55 laboratory test shots and 67 field test shots.

Jan 1, 1974

By H. V. Scotland

Lafarge Corporation&apos;s Texas Quarry, in Baltimore MD, achieved a substantial expansion of pit reserves by removing an inactive underground mine. The daylighting program, designed, and completed in 1997, open pit mined more than400 meters of room and pillar workings which were originally developed to recover high brightness Calcium Carbonate. The project proved to be a challenge throughout its course as the pit plan was modified and successful daylighting techniques were developed to remove the mine without adversely affecting the safety of the operation, quality of the stone recovered, or negatively impacting the surrounding community. The design parameters and techniques developed and implemented at Texas may prove of interest to other operators as they are faced with daylighting opportunities. This article will detail the challenges we faced and the solutions which made the project a success.

Jan 1, 1999

By R. M. Wheeler

For years the blasting industry has recognized eight milliseconds as the minimum delay time interval required between charges in order for them to be considered to fire independently of each other. However, computer analyses of seismic recordings made of several surface mine blasts reveals that this time interval may not always be sufficient for adequate vibration separation to occur. In some situations a combination of short delay periods and low frequency vibrations can result in waveform reinforcement. Various analyses of seismic recordings obtained from single hole detonations can be used to predict delay intervals that may enhance or reduce blast vibration effects.

Jan 1, 1987

By Robert A. Haney, David J. Atchison, Kenneth G. Fields

Mining systems with greater than a 20-foot face advance (deep cut) have become popular due to their increased productivity and safety. The face dust collection system used in many of the mines employing the deep cut systems, incorporates a machine mounted dust collector with either a blowing or exhausting line brattice and a remote control operated continuous miner. In order to characterize and quantify the parameters used to control dust with these systems, the Dust Division conducted studies on four mining sections using continuous miners with deep cut mining systems. On each section, the dust control system incorporated line brattice with a machine mounted dust collector. The remote control made it possible for the continuous mining machine to advance further while permitting the operator to remain under supported roof and away from dust generated during mining. The purpose of these studies was to evaluate the effectiveness of deep cut mining systems using dust collectors to control respirable dust exposure. This paper summarizes the results of the studies conducted. At each mine face workers were sampled to determine their full-shift dust exposure. Additionally, fixed point dust samples were collected at various locations to determine relative concentrations of dust generated from mining. Air quantities were measured at each working place to determine the amount of air delivered to the face area. Evaluations were made by comparing worker exposures to respirable dust samples taken at appropriate locations upstream and downstream of the coal faced being mined. An estimate of the amount of the respirable dust being generated at the face during mining and the amount of respirable dust being removed by the dust collectors was made by balancing the air quantities and the dust concentrations immediately upstream and downstream of the coal face. Results of the studies showed that the dust control systems, were effective for controlling workers exposure to respirable dust. Dust collector efficiencies were determined to be approximately 85 percent. While the dust collectors were effective in removing respirable dust, the success of the systems with line brattice greater than twenty feet from the face, was dependent on the use of the remote control which permitted the continuous miner operator to remain out of the high concentration dust cloud in the working face. Dilution from intake air, combined with the dust collector efficiency, maintained exposure of other section workers below applicable standards.

Jan 1, 1991

By D. A. Kramer

Seawater and natural brines accounted for about 51percent of U.S. magnesium compounds production during 2004. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties from well brines in Michigan. Caustic-calcined magnesia was recovered from sea-water by Premier Chemicals in Florida; from well brines in Michigan by Martin Marietta and Rohm and Haas; and from magnesite in Nevada by Premier Chemicals. Intrepid Mining and Great Salt Lake Minerals recovered magnesium chloride brines from the Great Salt Lake in Utah.

Jan 1, 2005

By R. D. Doepker, P. L. Drake

The dissolution of metals from various metal- mine tailings has been studied through a series of submerged tailings batch tests at US Bureau of Mines laboratories. Tailings selected for this study included both reactive (as determined by column leaching studies) and benign tailings. Metal mobilization in aerated (97% saturated with oxygen) samples appeared to be consistently greater than metal dissolution from stagnant (79% or 70% saturated with oxygen) waters. In the early weeks of the study, sulfate concentrations increased with solid-liquid contact time, while calcium dissolution remained early constant. Metal concentrations varied in relation to solid-liquid contact time and aeration. Leachate pH appeared to be nearly independent of solid-liquid contact time for basic tailings. Reactive tailings having both a submerged and a surface component demonstrated increased metal mobility.

Jan 1, 1991